The invention relates generally to semiconductor devices, and more particularly, to a method for doping spherical-shaped semiconductors.
The doping process involves the controlled introduction of an impurity to a substrate, which produces subtle changes in the electrical resistivity of the material. Such characteristics are necessary for solid-state electronic semiconductor devices, such as the transistor.
In the conventional semiconductor industry, a doped silicon substrate is created by adding the doping impurity directly into the melt during the crystal-pulling process. The final crystal is a uniformly doped one, from which wafers may be cut to serve as doped substrates.
In the case of spherical semiconductors, the single crystal substrates are not produced from a melt, but rather are made by remelting polycrystalline silicon granules which are grown by gas-phase reaction in a fluidized bed reactor. The random and turbulent nature of the fluidized bed process makes the attainment of sample-to-sample doping uniformity difficult. Therefore, the granules cannot be doped during growth in the fluidized bed, and must be doped by external means.
In U.S. Pate. Nos. 5,278,097, 5,995,776, and 5,223,452, methods and apparatuses for doping spherical-shaped semiconductors are disclosed. However, an improved method of doping the spherical shaped semiconductors, which is simpler and more economical, is desired.
The present invention, accordingly, provides a method for doping spherical semiconductors. To this end, one embodiment provides a receiver for receiving semiconductor spheres and a dopant powder. The semiconductor spheres and dopant powder are then directed to a chamber defined within an enclosure. The chamber maintains a heated, inert atmosphere with which to diffuse the dopant properties of the dopant powder into the semiconductor spheres.
In one embodiment, the method of doping a plurality of spherical shaped semiconductors includes: embedding the plurality of spherical shaped semiconductors in a dopant mixture to produce a powder mixture; heating the powder mixture to produce a plurality of doped spherical shaped semiconductors; cooling the doped spherical shaped semiconductors; removing the doped spherical shaped semiconductors from the powder mixture; and chemically etching the doped spherical shaped semiconductors.
In one embodiment, the plurality of spherical shaped semiconductors are made from a commercially available semiconductor material.
In one embodiment, the plurality of spherical shaped semiconductors are p-type spherical single crystal substrates.
In one embodiment, the plurality of spherical shaped semiconductors are n-type spherical single crystal substrates.
In one embodiment, the plurality of spherical shaped semiconductors are oxidized spherical shaped semiconductors.
In one embodiment, the dopant mixture is a mixture of a dopant oxide and silicon dioxide.
In one embodiment, the dopant mixture is a dopant nitride.
In one embodiment, the dopant mixture is a mixture of antimony oxide/silicon dioxide (Sb2O3/SiO2).
In one embodiment, the dopant mixture is a mixture of boric oxide/silicon dioxide (B2O3/SiO2).
In one embodiment, heating the powder mixture comprises diffusion and/or viscous flow along the surface of the spherical shaped semiconductors.
In one embodiment, the dopant mixture is boron nitride (BN).
In one embodiment, the method is done in a non-oxidizing environment.
In one embodiment, the method further includes melting the doped spherical shaped semiconductors to produce uniformly doped spherical shaped semiconductors and cooling the uniformly doped spherical shaped semiconductors.